A high-precision laser driver circuit and a control method thereof

Abstract

The application relates to the technical field of laser driver, and provides a high-precision laser driver circuit and a control method thereof. The circuit comprises a main control module, a DAC control module, a driving voltage generation module, a constant current driving module and a feedback module. The main control module outputs a control signal to the DAC control module. The DAC control module comprises first and second digital-to-analog conversion units. The first digital-to-analog conversion unit outputs a first analog voltage as a reference voltage, and the second digital-to-analog conversion unit outputs a second analog voltage as a bias voltage. Both the reference voltage and the bias voltage are connected to the driving voltage generation module. The driving voltage generation module generates and outputs a driving voltage according to the reference voltage and the bias voltage. The constant current driving module converts the driving voltage into corresponding laser driving current to drive the laser to emit laser, and outputs the current to the feedback module. The feedback module outputs a sampling voltage signal to the main control module. The main control module adjusts the analog voltages output by the two digital-to-analog conversion units according to the sampling voltage signal.

Description

Technical Field

[0001] This application relates to the field of laser driving technology, and in particular to a high-precision laser driving circuit and its control method. Background Technology

[0002] Currently, in the field of laser gas detection, VCSEL lasers are widely used as the core light source for gas concentration detection due to their inherent low power consumption, high sensitivity, and excellent operational stability.

[0003] In VCSEL laser driving schemes, dedicated VCSEL driver chips are commonly used to control the laser drive current. However, these dedicated driver chips have significant limitations: on the one hand, dedicated chips are specific to a particular application and have high manufacturing costs, resulting in high hardware costs for the entire detection system; on the other hand, their functional modules are fixed and have poor expandability. When high-precision output or stable operation of the device over a wide temperature range is required, the performance of dedicated chips often fails to meet stringent technical specifications.

[0004] To address the aforementioned issues, there is an urgent need to propose a laser driving circuit and its control method that can achieve precise and stable control of the VCSEL laser driving current while reducing hardware costs, improving functional expandability, and adapting to high-precision, wide-temperature-range gas detection scenarios. Summary of the Invention

[0005] To address the aforementioned issues, this application proposes a high-precision laser driving circuit and its control method. This method enables precise and stable control of the VCSEL laser driving current while reducing hardware costs, improving functional expandability, and adapting to high-precision, wide-temperature-range gas detection scenarios. The specific technical solution is as follows: In a first aspect, embodiments of this application propose a high-precision laser driving circuit, including a main control module, a DAC control module, a driving voltage generation module, a constant current driving module, and a feedback module. The output terminal of the main control module is connected to the input terminal of the DAC control module for outputting control signals; The DAC control module includes a first digital-to-analog converter (DAC) unit and a second DAC unit. The output terminal of the first DAC unit is connected to the first input terminal of the drive voltage generation module for outputting a first analog voltage. The output terminal of the second DAC unit is connected to the second input terminal of the drive voltage generation module for outputting a second analog voltage. The first analog voltage is the reference voltage of the laser drive current, and the second analog voltage is the bias voltage of the laser drive current. The output terminal of the driving voltage generation module is connected to the input terminal of the constant current driving module, and is used to generate and output the driving voltage corresponding to the laser driving current according to the reference voltage and the bias voltage. The output terminal of the constant current drive module is connected to the input terminal of the feedback module, and is used to convert the input drive voltage into a corresponding laser drive current to drive the laser to emit laser light. The output of the feedback module is connected to the input of the main control module, and is used to collect the laser drive current and output a corresponding sampling voltage signal to the main control module, so that the main control module can adjust the first analog voltage and the second analog voltage output by the DAC control module according to the sampling voltage signal.

[0006] Furthermore, the communication interface of the first digital-to-analog converter is an SPI communication interface, and the communication interface of the second digital-to-analog converter is an I²C communication interface, which are respectively connected to the corresponding communication pins of the main control module through the corresponding communication interfaces.

[0007] Furthermore, the DAC control module also includes a reference voltage output module composed of a current-limiting resistor, a capacitor, and a voltage reference chip. The input terminals of the reference voltages of the first digital-to-analog converter and the second digital-to-analog converter are both connected to the output terminal of the reference voltage output module.

[0008] Furthermore, the driving voltage generation module includes a four-stage operational amplifier circuit; The first-stage operational amplifier circuit is a voltage follower circuit. The non-inverting input terminal of the first-stage operational amplifier circuit is used as the first input terminal to connect to the reference voltage, and the output terminal is connected to the inverting input terminal of the second-stage operational amplifier circuit to achieve impedance isolation between the DAC control module and the subsequent circuit. The second-stage operational amplifier circuit is a voltage inverting circuit. The non-inverting input terminal of the second-stage operational amplifier circuit is connected to a reference voltage source, and the output terminal is connected to the inverting input terminal of the third-stage operational amplifier circuit. This is used to invert the output voltage of the first-stage operational amplifier circuit with the reference voltage provided by the reference voltage source as the center. The third-stage operational amplifier circuit is a voltage conversion circuit. The inverting input terminal of the third-stage operational amplifier circuit is used as the second input terminal to connect to the bias voltage, the non-inverting input terminal is connected to the reference voltage source, and the output terminal is connected to the non-inverting input terminal of the fourth-stage operational amplifier circuit, which is used to realize level inversion and superposition of the bias voltage. The fourth-stage operational amplifier circuit is a low-pass filter and buffer amplifier circuit. The output terminal of the fourth-stage operational amplifier circuit is connected to the constant current drive module, which is used to perform low-pass filtering and proportional amplification on the output voltage of the third-stage operational amplifier circuit to obtain the drive voltage, and to achieve impedance isolation from the subsequent circuit.

[0009] Furthermore, the constant current driving module includes a first operational amplifier and a sampling resistor. The sampling resistor is connected in series in the current loop of the laser driving circuit. One end of the sampling resistor is connected to the inverting input terminal of the first operational amplifier, and the output terminal of the fourth-stage operational amplifier circuit is connected to the non-inverting input terminal of the first operational amplifier, which is used to linearly convert the driving voltage output by the fourth-stage operational amplifier circuit into the corresponding laser driving current.

[0010] Furthermore, the feedback module includes a first voltage follower sampling unit and a second voltage follower sampling unit; The first voltage follower sampling unit includes a second operational amplifier, and the non-inverting input terminal of the second operational amplifier is connected to the high potential terminal in the current loop of the laser driving circuit through a first resistor; The second voltage follower sampling unit includes a third operational amplifier, the non-inverting input of which is connected to a low-potential terminal in the current loop of the laser driver circuit via a second resistor.

[0011] Secondly, embodiments of this application propose a control method for a high-precision laser driving circuit, applied to the high-precision laser driving circuit described in any one of the first aspects, the method comprising: The DAC control module receives control signals output by the main control module; the DAC control module includes a first digital-to-analog converter unit and a second digital-to-analog converter unit. The DAC control module includes a first digital-to-analog converter unit that converts the corresponding control signal into a first analog voltage and inputs it to the first input terminal of the drive voltage generation module. The DAC control module also includes a second digital-to-analog converter unit that converts the corresponding control signal into a second analog voltage and inputs it to the second input terminal of the drive voltage generation module. The first analog voltage is the reference voltage of the laser drive current, and the second analog voltage is the bias voltage of the laser drive current. The driving voltage generation module generates and outputs the driving voltage corresponding to the laser driving current based on the reference voltage and the bias voltage. The constant current drive module receives the drive voltage, converts the drive voltage into a corresponding laser drive current to drive the laser to emit laser light, and outputs the laser drive current to the feedback module. The feedback module acquires the laser drive current, converts the laser drive current into a corresponding sampling voltage signal, and feeds it back to the main control module, so that the main control module adjusts the first analog voltage and the second analog voltage output by the DAC control module according to the sampling voltage signal.

[0012] Furthermore, the driving voltage generation module includes a four-stage operational amplifier circuit; The step of the driving voltage generation module generating and outputting the driving voltage corresponding to the laser driving current based on the reference voltage and the bias voltage includes: The non-inverting input of the first-stage operational amplifier circuit serves as the first input, receiving the reference voltage output by the DAC control module and performing voltage following processing to obtain the following voltage, thereby achieving impedance isolation between the DAC control module and the subsequent circuit. The second-stage operational amplifier circuit, based on the reference voltage provided by the reference voltage source, inverts the follower voltage output by the first-stage operational amplifier circuit to obtain the first output voltage. The inverting input terminal of the third-stage operational amplifier circuit is used as the second input terminal, and the bias voltage output by the DAC control module is connected to it. At the same time, the first output voltage is also connected to it. Based on the bias voltage and the first output voltage, the second output voltage is generated. The fourth-stage operational amplifier circuit performs low-pass filtering and proportional amplification on the second output voltage to obtain the driving voltage and achieves impedance isolation from the subsequent circuit.

[0013] Furthermore, the step of the second-stage operational amplifier circuit inverting the follower voltage output by the first-stage operational amplifier circuit based on the reference voltage provided by the reference voltage source to obtain the first output voltage includes: Based on the reference voltage VREF provided by the reference voltage source and the follower voltage Vin output by the first-stage operational amplifier circuit, the first output voltage Vout1 is calculated according to the following formula: Vout1=VREF-(Vin-VREF)=2VREF-Vin.

[0014] Further, the step of generating a second output voltage based on the bias voltage and the first output voltage includes: Based on the bias voltage VI_set2 and the first output voltage Vout1, the second output voltage Vout2 is calculated according to the following formula: Vout2=-(A x Vout1+B x VI_set2)+C; Wherein, A, B, and C are constants determined by the peripheral resistor network of the third-stage operational amplifier circuit, the absolute value of A is less than 1, and A and B are positive numbers.

[0015] The high-precision laser driving circuit and its control method provided in this application have the following advantages: 1. Low cost and scalability: By designing the driver circuit independently, the dependence on VCSEL dedicated driver chips is effectively reduced, which can reduce the cost of using dedicated chips and thus reduce the hardware cost of laser gas detection equipment. At the same time, the parameters of the DAC control module can be flexibly adjusted according to the gas concentration detection requirements, improving the scalability and scene adaptability of the driver circuit.

[0016] 2. Flexible adaptability and high reliability: Based on the design of dual-channel independent output voltage of DAC control module and multi-stage operational amplifier division of labor, it can realize high-precision closed-loop control of laser drive current, meet the high-precision requirements of laser gas detection, and combined with the design of independent generation and flexible superposition of base voltage and bias voltage, it supports arbitrary starting point and arbitrary waveform scanning output, thereby improving the accuracy and stability of gas concentration detection.

[0017] 3. Adaptable to wide temperature range scenarios: It solves the problems of unstable operation and accuracy degradation of VCSEL dedicated driver chips under extreme temperature ranges, and enhances the environmental adaptability and reliability of the driver circuit. Attached Figure Description

[0018] Figure 1 This is a structural block diagram of a high-precision laser driving circuit provided in this application; Figure 2 This is a circuit diagram of a first digital-to-analog converter unit provided in this application; Figure 3 This is a circuit diagram of a second digital-to-analog converter unit provided in this application; Figure 4 This is a circuit diagram of a driving voltage generation module provided in this application; Figure 5 This is a circuit diagram of a constant current drive module provided in this application; Figure 6 This is a circuit diagram of a feedback module provided in this application; Figure 7 This is a flowchart of a control method for a high-precision laser driving circuit provided in this application. Detailed Implementation

[0019] To make the technical problems solved by this application, the technical solutions adopted, and the technical effects achieved clearer, this application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit it.

[0020] This application provides a high-precision laser driving circuit, such as... Figure 1 As shown, the driving circuit includes a main control module, a DAC control module, a driving voltage generation module, a constant current driving module, and a feedback module.

[0021] The output of the main control module is connected to the input of the DAC control module to output control signals. In one implementation, the main control module can be implemented using a microcontroller, sending control signals to the DAC control module via a pin-based communication interface.

[0022] The DAC control module may include a first digital-to-analog converter (DAC) unit and a second DAC unit. The output terminal of the first DAC unit is connected to the first input terminal of the drive voltage generation module and is used to output a first analog voltage, which is the reference voltage of the laser drive current. The output terminal of the second DAC unit is connected to the second input terminal of the drive voltage generation module and is used to output a second analog voltage, which is the bias voltage of the laser drive current.

[0023] Since the DAC control module integrates two independent digital-to-analog converters, the main control module can synchronously output two independent control signals to drive the two digital-to-analog converters respectively, so as to generate two analog voltages that do not interfere with each other. That is, the first analog voltage is generated by the first digital-to-analog converter and the second analog voltage is generated by the second digital-to-analog converter.

[0024] In one embodiment, the DAC control module may further include a reference voltage output module composed of a current-limiting resistor, a capacitor, and a voltage reference chip. The input terminals of the reference voltages of both the first digital-to-analog converter and the second digital-to-analog converter are connected to the output terminal of the reference voltage output module. The current-limiting resistor and capacitor connected to the output terminal of the voltage reference chip constitute an RC filter circuit.

[0025] Both the first and second digital-to-analog converters can employ 16-bit high-precision DAC chips. Therefore, the DAC control module, centered on this 16-bit high-precision DAC and paired with a low-noise, low-temperature-drift voltage reference source provided by the reference voltage output module, achieves high-precision, high-linearity conversion of digital signals to analog voltage. Its theoretical resolution reaches 38μV, enabling fine adjustment and precise control of the output voltage. Furthermore, the high-precision analog voltage output can serve as a pre-amplitude reference for a high-stability voltage-controlled current source, providing the entire closed-loop control system with milliampere- to microampere-level precision current drive capability.

[0026] In one implementation, the communication interface of the first digital-to-analog converter unit can be an SPI communication interface to meet the requirement of rapid data interaction with subsequent modules. The communication interface of the second digital-to-analog converter unit can be an I²C communication interface to meet the requirement of high-precision voltage control. Both units are connected to the corresponding communication pins of the main control module through their respective communication interfaces.

[0027] The main control module outputs digital control signals to the DAC control module via a communication interface. Specifically, the main control module can output a first control signal to the first digital-to-analog converter unit to set the reference voltage, and a second control signal to the second digital-to-analog converter unit to set the bias voltage, through corresponding communication pins, so as to achieve synchronous output of the two analog signals.

[0028] This application provides a DAC control module, referencing... Figures 2-3 The first digital-to-analog converter (DAC) unit includes a DAC chip U0, which can be an AD5662. The second DAC unit includes a DAC chip U4, which can be an AD5693. The reference voltage output module includes a voltage reference chip U5, which can be an LM4041.

[0029] U0 is used to output the first analog voltage I_SET1, which is then connected to the first input terminal of the subsequent drive voltage generation module. VDD (pin 1) is connected to a 3.3V analog power supply (A3V3) to power the chip, and shares the same analog power supply with U4 and U5 to reduce noise crosstalk between different power supplies and ensure stable operation of the analog circuit. VREF (pin 2) is connected to the output terminal of U5, sharing the 1.225V (i.e., VREF1.225) high-precision reference voltage provided by U5 with U4, ensuring that the voltage references of the two digital-to-analog conversion units are consistent and avoiding DAC output voltage deviation caused by reference voltage differences.

[0030] VFB (pin 3) is connected to VOUT (pin 4) to form a voltage follower closed loop, ensuring stable output voltage. U0's communication interface is an SPI interface. SYNC# (pin 5) is connected to the SPI2_CS pin of the main control module for chip select enable and synchronization control. SCLK (pin 6) is connected to the SPI2_SCK pin of the main control module as the clock line for SPI communication, synchronizing digital signal transmission between the main control module and the chip. DIN (pin 7) is connected to the SPI2_MISO pin of the main control module as the data line for SPI communication, used to send 16-bit data to U0 to complete SPI communication configuration and perform the corresponding analog voltage conversion. GND (pin 8) is connected to system ground, sharing a common ground with the ground pin of U5 and the GND (pin 5) of U4, ensuring consistent ground references for the entire module and eliminating interference caused by ground potential differences.

[0031] U4's VDD (pin 1), VLOGIC (pin 2), and RESET# (pin 3) are all connected to a 3.3V analog power supply (A3V3). LDAC# (pin 4) and A0 (pin 6) are both grounded. U4's communication interface is I... 2 The C communication interface, SCL (pin 7) is connected to the I2C1_SCL pin of the main control module, as an I... 2 The clock line for C-communication synchronizes the digital signal transmission between the main control module and the chip. SDA (pin 8) connects to the I2C1_SDA pin of the main control module, serving as the I2C1 clock line. 2 The C-type communication data line is used to receive 16-bit digital control words output by the main control module. Pins 7 and 8 can be connected to a 3.3V power supply via pull-up resistors R16 and R17 to ensure stable and reliable communication signals. The pull-up resistor value can be 5.1kΩ, and no specific limitation is made here.

[0032] VREF (pin 9) is connected to the output of the LM4041 to receive the 1.225V reference voltage output by the LM4041. VOUT (pin 10) outputs the second analog voltage I_SET2, which is connected to the subsequent drive voltage generation module. Working in conjunction with the first DAC output signal, it enables fine adjustment of the laser drive voltage to meet the system's wide-range detection control requirements. R13 and C14 form a low-pass filter, which, through filtering, noise reduction, and impedance matching, makes the output analog voltage smoother and more accurate. The values ​​of R13 and C14 can be set according to actual needs and are not specifically limited here.

[0033] Both capacitor C0 in the first digital-to-analog converter unit and capacitor C13 in the second digital-to-analog converter unit are grounding capacitors, which can serve functions such as voltage stabilization and filtering. The capacitance value of the grounding capacitor can be 100nF, and no specific limitation is made here.

[0034] U5 provides a stable reference voltage for the DAC control module. Its floating terminal should not be connected to any signal to prevent irrelevant signals from interfering with the chip's normal operation. With the current-limiting resistor R11, it operates within its rated current range, outputting a high-precision, low-noise 1.225V reference voltage. A capacitor C15 can be connected in parallel between the output of U5 and system ground to suppress high-frequency noise in the reference voltage, filter out interference from power supply fluctuations, and further improve the stability of the reference voltage input to the VREF pins of the two digital-to-analog converter units.

[0035] After the DAC control module outputs the reference voltage and bias voltage, the drive voltage generation module can generate and output the drive voltage of the laser drive current based on the reference voltage and bias voltage, so as to output to the subsequent constant current drive module.

[0036] In one embodiment, the drive voltage generation module includes a four-stage operational amplifier circuit, namely a first-stage operational amplifier circuit, a second-stage operational amplifier circuit, a third-stage operational amplifier circuit, and a fourth-stage operational amplifier circuit. Each stage of the operational amplifier circuit can use the same operational amplifier.

[0037] The first-stage operational amplifier circuit is a voltage follower circuit, meaning it uses a voltage follower structure. Its non-inverting input serves as the first input, connected to the reference voltage (i.e., the first analog voltage) output by the DAC control circuit. This voltage follower structure achieves impedance isolation between the DAC control module and subsequent circuits, preventing the subsequent circuits from affecting the output voltage of the preceding DAC stage and ensuring the accuracy and stability of the first analog voltage. Its output is connected to the inverting input of the second-stage operational amplifier circuit, and the inverting input is directly connected to the output.

[0038] The second-stage operational amplifier circuit is a voltage inverting circuit. Its non-inverting input is connected to a reference voltage source, using the reference voltage provided by the source as the output reference level. The output of the first-stage operational amplifier circuit is connected to the inverting input of the second-stage operational amplifier circuit. This allows the second-stage operational amplifier circuit to invert the output voltage of the first-stage operational amplifier circuit, using the reference voltage provided by the source as the center. This provides a fundamental guarantee for achieving rail-to-rail output swing in the overall circuit. In other words, the output voltage of the second-stage operational amplifier circuit is symmetrically inverted relative to the reference voltage, just like the output voltage of the first-stage operational amplifier circuit.

[0039] In one implementation, the second-stage operational amplifier circuit can connect its non-inverting input to the reference voltage output module in the DAC control circuit, meaning the entire driving circuit uses the same reference voltage. The output of the second-stage operational amplifier circuit is connected to the inverting input of the third-stage operational amplifier circuit.

[0040] The third-stage operational amplifier circuit is a voltage conversion circuit. Its inverting input terminal serves as the second input terminal, receiving a bias voltage and the output voltage of the second-stage operational amplifier circuit. The input signal is inverted through an internal resistor network, and the bias voltage is superimposed on the output signal to achieve signal polarity adjustment, level offset, and amplitude adaptation. This ensures that the output voltage meets the input range requirements of the subsequent circuits and can support scanning of arbitrary starting points and arbitrary waveforms.

[0041] The fourth-stage operational amplifier circuit is a low-pass filter and buffer amplifier circuit. Its output is connected to the constant current drive module, which is used to perform low-pass filtering and proportional amplification on the output voltage of the third-stage operational amplifier circuit to obtain the drive voltage, and to achieve impedance isolation from the subsequent circuit.

[0042] This application provides a driving voltage generation module, such as... Figure 4As shown, this module consists of four cascaded operational amplifier circuits, with each stage using an RS8564XQ operational amplifier.

[0043] The first-stage operational amplifier circuit includes U7A, which, together with capacitor C20 and resistor R27, forms a unity-gain voltage follower as a voltage buffer. I_SET1 is connected to the non-inverting input of U7A through resistor R27. The output of U7A is directly fed back to the inverting input of the next operational amplifier, U7B, forming deep negative feedback. The positive power supply is connected to an A3V3 analog power supply, and the negative power supply is grounded. Capacitor C20 is a grounding capacitor, which can suppress power supply noise and improve stability. This circuit effectively isolates the input voltage from the subsequent load, improving the system linearity and drive capability.

[0044] The second-stage operational amplifier circuit includes U7B, capacitor C17, and resistor R22. Capacitor C17 and resistor R22 form a low-pass filter, which suppresses high-frequency noise in the circuit and simultaneously achieves phase compensation, preventing self-oscillation during operation. As one implementation, if the non-inverting input of this second-stage operational amplifier circuit is connected to a reference voltage VREF, and the inverting input is connected to the output voltage Vin of the preceding stage circuit, based on VREF and Vin, and according to the operating principle of operational amplifiers, the first output voltage Vout1 of the second-stage operational amplifier circuit can be calculated using the following formula: Vout1=VREF-(Vin-VREF)=2VREF-Vin.

[0045] If the reference voltage VREF is set to 1.225V, then the level inversion and offset centered on 1.225V can be achieved by using the formula Vout1=2.45V-Vin, thereby obtaining the first output voltage Vout1 that meets the system requirements.

[0046] When the operational amplifier is operating normally, the highest value of the first output voltage is no less than the supply voltage minus 100mV, and the lowest value is no more than the supply voltage plus 100mV. Those skilled in the art will understand that this difference depends on the specific operational amplifier model and its output stage characteristics. This operational amplifier stage provides a fundamental guarantee for rail-to-rail power supply.

[0047] The third-stage operational amplifier circuit includes U7C, capacitor C18, and resistor R25. Capacitor C18 and resistor R25 form a low-pass filter. This circuit not only performs proportional attenuation of the input signal but also achieves level inversion and DC bias adjustment functions through an inverting input bias voltage I_SET2.

[0048] In one implementation, after processing by this stage of the circuit, the second output voltage Vout2 can satisfy the following relationship: Vout2 = -(A x Vout1 + B x VI_set2) + C, where A, B, and C are constants determined by the external resistor network of the third-stage operational amplifier circuit, the absolute value of A is less than 1, and A and B are positive numbers. By configuring the above coefficients, the output voltage Vout2 can meet the requirements of the subsequent circuit for amplitude, polarity, and DC bias. Specifically, the configuration of the coefficients is related to the settings of resistors R26, R25, and R14, and can be set according to requirements.

[0049] For example, if R26 is 10K, R25 is 1K, and R14 is 2.2K, we can calculate Vout2 = 1.225-0.1x(Vout1-1.25)-0.4545x(VI_set2-1.225). That is, the circuit attenuation ratio is 10 times. When the value of VI_set2 increases, the overall waveform decreases. When the value of VI_set2 decreases, the overall waveform increases.

[0050] Connecting pull-up resistors R31 and R32 to the non-inverting input terminals of the second-stage and third-stage operational amplifier circuits can ensure the stability of the operational amplifier's static operating point and suppress output drift and noise.

[0051] The fourth-stage operational amplifier circuit includes U7D, which is a combination of second-order low-pass filter, voltage follower, and proportional amplifier circuits. It is used to smooth and filter the front-end signal, perform anti-interference processing, and output a stable control signal to the constant current drive circuit, i.e., the output drive voltage V. LD_Ctr The signal is directed to the constant current drive circuit. The non-inverting input of U7D receives the second output voltage from the preceding stage via resistor R28. Simultaneously, a 1.225V reference voltage VREF is provided with DC bias via resistor R19 to prevent negative output voltage. Resistor R24 ​​and capacitor C19, and resistor R30 and capacitor C26, respectively constitute two stages of first-order RC low-pass filter circuits to filter out high-frequency noise and interference in the signal. Their cutoff frequency is set to 15.6 kHz to ensure signal bandwidth and smoothness.

[0052] Resistors R29 and R30, and R24 and R23 form a voltage feedback network to determine the closed-loop gain of the operational amplifier. Taking R29 as 56Ω and R30 as 1kΩ, the non-inverting gain Av is calculated to be 1 + R30 / R29 = 1.056. This gain is close to 1, making this stage of the circuit equivalent to a voltage follower with slight gain adjustment. This allows the output voltage to closely match the input control voltage, significantly improving the circuit's driving capability, load-driving capacity, and signal stability.

[0053] The driving voltage generation module provided in this embodiment achieves multi-stage operational amplifier cascade through multiple operational amplifiers, and uses low-cost chips to buffer, invert, superimpose, and adjust the gain of the DAC output signal, ultimately converting it into a driving voltage. This module can support high-precision, continuous scanning output of arbitrary waveform signals. At the same time, by selecting low-temperature drift, low-offset operational amplifiers and high-precision, high-stability sampling resistor-capacitor components, it effectively suppresses temperature drift and noise interference, ensuring the output accuracy and operational stability of the driving circuit under long-term working conditions.

[0054] The driving voltage is input to the constant current driving module, and the output of the constant current driving module is connected to the input of the feedback module. This module converts the driving voltage into the corresponding laser driving current, providing a stable and reliable driving signal to drive the laser to emit laser light.

[0055] The constant current drive module includes a first operational amplifier and a sampling resistor. The sampling resistor is connected in series in the current loop of the laser drive circuit to detect the laser's operating current. The output of the fourth-stage operational amplifier circuit is connected to the non-inverting input of the first operational amplifier, and one end of the sampling resistor is connected to the inverting input of the first operational amplifier. That is, the voltage across the sampling resistor is fed back to the inverting input of the first operational amplifier, forming a closed-loop feedback structure of the voltage-controlled constant current source together with the drive voltage at the non-inverting input. In this way, the first operational amplifier linearly converts the drive voltage output from the fourth-stage operational amplifier circuit into the corresponding laser drive current based on the set voltage at the non-inverting input.

[0056] In other words, the voltage across the sampling resistor is proportional to the laser drive current. The inverting input of the first operational amplifier is connected to the output of the sampling resistor, and the non-inverting input is connected to the drive voltage output from the fourth-stage operational amplifier circuit. The first operational amplifier uses its virtual short characteristic to linearly convert the drive voltage into the corresponding constant laser drive current. Furthermore, a decoupling capacitor is connected to the input of the sampling resistor.

[0057] This application provides a constant current driving module, such as... Figure 5 As shown, U3A can use an RS8564XQ operational amplifier. Based on the virtual short characteristic of the operational amplifier, precise current control can be achieved, meaning the voltage at the non-inverting input of U3A always remains equal to the voltage at the inverting input. This determines the laser drive current I. LD The core computational relationship is I LD = V LD_Ctr / R12, realizes the laser drive current I LD With driving voltage V LD_Ctr Linear binding.

[0058] This module may also include a voltage-driven MOSFET Q2. The negative feedback closed-loop control circuit established by this module allows U3A to compare the drive voltage at the non-inverting input terminal with the output voltage in real time, and output the result to the gate of Q2. When the output voltage is less than the drive voltage, the output voltage of U3A increases, enhancing the conduction of Q2 and thus increasing the laser drive current I. LD When the output voltage is greater than the driving voltage, the output voltage of U3A decreases, weakening the conduction of Q2 and thus reducing the laser driving current I. LD Dynamic balance is achieved through continuous negative feedback adjustment, stabilizing the laser's operating drive current. Simultaneously, resistor R15 in the circuit acts as a damper to suppress oscillations, significantly improving the operational stability of the drive circuit. Capacitor C12 is a grounding capacitor, serving both voltage stabilization and filtering functions.

[0059] This module uses the negative feedback of the operational amplifier to make the voltage across the sampling resistor follow the control voltage change, thereby linearly converting the input voltage into a stable output current and achieving high-precision constant current drive.

[0060] The feedback module collects the laser drive current at both ends of the laser in the constant current drive module, converts it into a corresponding sampling voltage signal, and outputs the sampling voltage signal to the main control module. When the main control module receives the sampling voltage signal, it compares the sampling voltage signal with the voltage corresponding to the preset laser drive current, and adjusts the output control signal according to the comparison result, thereby regulating the first analog voltage and the second analog voltage output by the DAC control module.

[0061] In one implementation, when the main control module receives the sampled voltage signal, it compares the sampled voltage signal with the voltage corresponding to the preset laser drive current, and adjusts the output control signal according to the comparison result, adjusting only the first analog voltage output by the DAC control module.

[0062] In one implementation, the feedback module may include a first voltage follower sampling unit and a second voltage follower sampling unit. The first voltage follower sampling unit includes a second operational amplifier, the non-inverting input of which is connected to the high potential end in the current loop of the laser driving circuit, i.e., the laser anode, through a first resistor. The second voltage follower sampling unit includes a third operational amplifier, the non-inverting input of which is connected to the low potential end in the current loop of the laser driving circuit, i.e., the laser cathode, through a second resistor. The two voltage signals are used to calculate the voltage difference across the sampling resistor.

[0063] In this embodiment, the first resistor and the second resistor have the same resistance value, and the first voltage follower sampling unit and the second voltage follower sampling unit have the same structure. In one implementation, the non-inverting input terminal of the second operational amplifier is connected to the laser anode through the first resistor, and the non-inverting input terminal of the third operational amplifier is connected to the laser cathode through the second resistor.

[0064] This application provides a feedback module, referencing... Figures 5-6 This module consists of two identical voltage follower sampling circuits used to acquire the voltage signal of the laser drive circuit in real time, thus providing a high-precision current feedback signal for the system's closed-loop control. Both operational amplifiers, U3B and U3C, adopt a voltage follower structure. The non-inverting input of U3B is connected to the low-potential sampling point in the laser drive circuit's current loop, i.e., the laser cathode LD- terminal, while the non-inverting input of U3C is connected to the high-potential sampling point in the laser drive circuit's current loop, i.e., the laser anode LD+ terminal.

[0065] The output of U3B is directly fed back to its own inverting input, and the output of U3C is also directly fed back to its own inverting input. Both operational amplifiers have low-pass filters with a cutoff frequency of 1.592kHz designed for their input and output terminals. Specifically, resistor R21 and capacitor C22 constitute the low-pass filter at the input of U3B, and resistor R20 and capacitor C21 constitute the low-pass filter at the output of U3B. Resistor R35 and capacitor C30 constitute the low-pass filter at the input of U3C, and resistor R33 and capacitor C29 constitute the low-pass filter at the output of U3C.

[0066] The filter design effectively smooths the input and output signals of the operational amplifier, filtering out high-frequency noise interference in the circuit and providing a low-ripple, high-stability voltage signal for subsequent sampling. The outputs of the two voltage followers are connected to the ADC sampling channels corresponding to the PC0 and PC3 pins of the microcontroller, respectively. The microcontroller acquires the buffered and filtered sampling voltage signals in real time and synchronously adjusts I_SET1 and I_SET2 to ultimately achieve dynamic closed-loop regulation of the laser drive current.

[0067] This application utilizes all general-purpose discrete components, eliminating the need for dedicated VCSEL driver chips. It enables high-precision microampere-level control of the laser drive current at low cost, offering exceptional flexibility and configurability. By adjusting the DAC output amplitude and peripheral circuit parameters, it can adapt to the threshold current and operating power requirements of different VCSEL models.

[0068] Furthermore, the technical solution adopted in this application, which uses a DAC combined with a multi-stage operational amplifier architecture to replace the traditional dedicated driver chip, achieves high-precision, flexible and controllable driving of VCSEL luminous intensity and scanning waveform through the coordinated work of modules such as voltage buffering, voltage-to-current conversion and current superposition. This can effectively solve the problem of excessive cost, while having customization and expansion capabilities far exceeding those of dedicated chips. The overall hardware cost is reduced by an order of magnitude compared to the traditional dedicated chip solution.

[0069] It should be noted that the resistance value of the resistor and the capacitance value of the capacitor set in each embodiment can be set according to actual needs, and no specific limitation is made here.

[0070] This application also provides a control method for a high-precision laser driving circuit, employing the high-precision laser driving circuit described in any of the above embodiments, such as... Figure 7 As shown, the method includes: S701, the DAC control module receives control signals output by the main control module.

[0071] The DAC control module includes a first digital-to-analog converter and a second digital-to-analog converter.

[0072] The DAC control module receives the control signal output by the main control module, performs digital-to-analog conversion on the control signal, and generates an analog voltage.

[0073] S702, the DAC control module includes a first digital-to-analog converter unit that converts the corresponding control signal into a first analog voltage and inputs it to the first input terminal of the drive voltage generation module. The DAC control module also includes a second digital-to-analog converter unit that converts the corresponding control signal into a second analog voltage and inputs it to the second input terminal of the drive voltage generation module.

[0074] The first analog voltage is the reference voltage for the laser drive current, and the second analog voltage is the bias voltage for the laser drive current.

[0075] S703, the drive voltage generation module generates and outputs the drive voltage corresponding to the laser drive current based on the reference voltage and bias voltage.

[0076] The drive voltage generation module receives the first analog voltage and the second analog voltage, namely the reference voltage and the bias voltage. Through the internal operational amplifier circuit, the two analog voltages are buffered, level converted and noise filtered, and finally output a stable drive voltage, providing the basic conditions for laser driving.

[0077] S704, the constant current drive module receives the drive voltage, converts the drive voltage into the corresponding laser drive current to drive the laser to emit laser light, and outputs the laser drive current to the feedback module.

[0078] The constant current drive module receives the drive voltage and linearly converts it into a constant laser drive current through an internal operational amplifier circuit and feedback adjustment circuit. At the same time, it utilizes the switching characteristics of the MOSFET to achieve precise control of the laser drive current and ensure its stability.

[0079] S705, the feedback module collects the laser drive current, converts the laser drive current into a corresponding sampling voltage signal, and feeds it back to the main control module so that the main control module can adjust the first analog voltage and the second analog voltage output by the DAC control module according to the sampling voltage signal.

[0080] The feedback module collects the sampling voltage signal corresponding to the laser drive current in real time. After filtering and noise reduction of the collected signal, it feeds it back to the main control module to provide the main control module with a precise current feedback signal.

[0081] In one implementation, the main control module receives a sampled voltage signal, compares the sampled voltage signal with the voltage corresponding to a preset laser drive current, and adjusts the output control signal according to the comparison result to regulate the first analog voltage and the second analog voltage output by the DAC control module.

[0082] In another implementation, when the main control module receives the sampled voltage signal, it compares the sampled voltage signal with the voltage corresponding to the preset laser drive current, and adjusts the output control signal according to the comparison result. Only the first analog voltage output by the DAC control module is adjusted to ensure that the laser drive current is stable within the preset range and to ensure stable laser emission.

[0083] The laser driver circuit control method provided in this application employs dual DACs to independently output reference and bias voltages, combined with a multi-stage operational amplifier circuit to achieve voltage buffering, level conversion, noise filtering, and drive capability adjustment, enabling the output of high-precision, arbitrary waveform drive signals. Through voltage-controlled constant current and a closed-loop feedback structure, drive errors are corrected in real time, suppressing the effects of temperature drift and device parameter dispersion, significantly improving the stability and output consistency of the laser drive current. Furthermore, the circuit is simple, low-cost, highly accurate, and reliable, meeting the requirements for long-term stable laser operation.

[0084] As one embodiment of this application, the driving voltage generation module includes a four-stage operational amplifier circuit, and each stage of the operational amplifier circuit can use the same operational amplifier. The step of the drive voltage generation module generating and outputting the drive voltage corresponding to the laser drive current based on the reference voltage and bias voltage may include: The non-inverting input of the first-stage operational amplifier circuit serves as the first input, receiving the reference voltage output from the DAC control module and performing voltage following processing to obtain the following voltage, thus achieving impedance isolation between the DAC control module and the subsequent circuits. The second-stage operational amplifier circuit, based on the reference voltage provided by the reference voltage source, inverts the following voltage output from the first-stage operational amplifier circuit to obtain the first output voltage. The inverting input of the third-stage operational amplifier circuit serves as the second input, receiving the bias voltage output from the DAC control module and the first output voltage, and generating the second output voltage based on the bias voltage and the first output voltage. The fourth-stage operational amplifier circuit performs second-order low-pass filtering and proportional amplification on the second output voltage to obtain the driving voltage, thus achieving impedance isolation between the second-stage operational amplifier circuit and the subsequent circuits.

[0085] The first-stage operational amplifier circuit is a voltage follower structure. Its non-inverting input serves as the first input of the module, connected to the reference voltage output by the DAC control module. This stage only provides impedance isolation for the reference voltage, without altering its amplitude or phase. This effectively isolates the mutual interference between the DAC control module and the subsequent operational amplifier circuit, preventing the load effect of the subsequent circuit from affecting the stability of the reference voltage.

[0086] The second-stage operational amplifier circuit is a voltage inverting structure. Its non-inverting input is connected to a preset reference voltage source, and its inverting input is connected to the output of the first-stage operational amplifier circuit, receiving the voltage output from the first stage. This stage circuit uses the reference voltage provided by the reference voltage source as its center, inverts the reference voltage signal output from the first stage, and accurately calculates and outputs a stable first output voltage through a preset resistor feedback network. This achieves phase adjustment of the reference voltage, providing a basis for subsequent level shifting and bias superposition.

[0087] The third-stage operational amplifier circuit is a voltage conversion structure. Its inverting input serves as the second input of the module, receiving the bias voltage from the DAC control module and the first output voltage from the second-stage operational amplifier circuit. This stage circuit, based on the amplitude and phase of the first output voltage, superimposes the bias voltage and performs level inversion, adjusting the signal polarity and DC level shifting to ensure the second output voltage meets the processing requirements of the fourth-stage circuit while also adapting to the laser drive voltage range.

[0088] The fourth-stage operational amplifier circuit is a low-pass filter and buffer amplification structure. It receives the second output voltage from the third-stage operational amplifier circuit and performs second-order low-pass filtering on the signal through an internal two-stage RC low-pass filter network. This effectively filters out high-frequency noise, interference signals, and harmonic components in the signal, ensuring signal smoothness. At the same time, the proportional amplifier circuit performs precise gain fine-tuning on the filtered signal to make the output voltage reach the amplitude required for laser driving and achieves impedance isolation from the subsequent constant current drive module, ultimately outputting a stable and accurate laser drive voltage.

[0089] As can be seen, in the embodiments of this application, the use of graded amplification and bias superposition design can accurately control the output voltage amplitude, ensure the stability of the laser drive current, and at the same time, the overall circuit design is simple, the cost is controllable, and it is suitable for the high precision and high stability requirements of the laser.

[0090] As one embodiment of this application, the step of the second-stage operational amplifier circuit inverting the follower voltage output by the first-stage operational amplifier circuit based on the reference voltage provided by the reference voltage source to obtain the first output voltage may include: Based on the reference voltage VREF provided by the reference voltage source and the follower voltage Vin output by the first-stage operational amplifier circuit, the first output voltage Vout1 can be calculated according to the following formula: Vout1=VREF-(Vin-VREF)=2VREF-Vin.

[0091] As can be seen, the second-stage operational amplifier circuit included in the drive voltage generation module can convert the reference voltage VREF into an inverted voltage according to the formula Vout1=2VREF-Vin. At the same time, it reduces noise interference through multi-stage filtering and, together with the closed-loop feedback structure, enables the drive voltage to be output stably.

[0092] As one embodiment of this application, the step of generating a second output voltage based on a bias voltage and a first output voltage may include: Based on the bias voltage VI_set2 and the first output voltage Vout1, the second output voltage Vout2 can be calculated using the following formula: Vout2= -(A x Vout1+B x VI_set2)+C; Wherein, A, B, and C are constants determined by the peripheral resistor network of the third-stage operational amplifier circuit, the absolute value of A is less than 1, and A and B are positive numbers.

[0093] This embodiment uses a clear calculation formula based on the first output voltage Vout1 and the bias voltage VI_set2. By precisely setting three parameters A, B, and C, the amplitude of Vout2 can be flexibly adjusted. This not only achieves attenuation adjustment of the first output voltage Vout1 but also accurately superimposes the bias voltage VI_set2, effectively avoiding signal distortion and ensuring the stability and accuracy of the second output voltage Vout2. At the same time, the coefficients can be flexibly adjusted according to actual needs to adapt to the voltage output requirements in different scenarios, improving the flexibility and accuracy of the driving voltage generation.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some or all of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A high-precision laser driving circuit, characterized in that, It includes a main control module, a DAC control module, a drive voltage generation module, a constant current drive module, and a feedback module; The output terminal of the main control module is connected to the input terminal of the DAC control module for outputting control signals; The DAC control module includes a first digital-to-analog converter (DAC) unit and a second DAC unit. The output terminal of the first DAC unit is connected to the first input terminal of the drive voltage generation module for outputting a first analog voltage. The output terminal of the second DAC unit is connected to the second input terminal of the drive voltage generation module for outputting a second analog voltage. The first analog voltage is the reference voltage of the laser drive current, and the second analog voltage is the bias voltage of the laser drive current. The output terminal of the driving voltage generation module is connected to the input terminal of the constant current driving module, and is used to generate and output the driving voltage corresponding to the laser driving current according to the reference voltage and the bias voltage. The output terminal of the constant current drive module is connected to the input terminal of the feedback module, and is used to convert the input drive voltage into a corresponding laser drive current to drive the laser to emit laser light. The output of the feedback module is connected to the input of the main control module, and is used to collect the laser drive current and output a corresponding sampling voltage signal to the main control module, so that the main control module can adjust the first analog voltage and the second analog voltage output by the DAC control module according to the sampling voltage signal.

2. The high-precision laser driving circuit according to claim 1, characterized in that, The communication interface of the first digital-to-analog converter is an SPI communication interface, and the communication interface of the second digital-to-analog converter is an I²C communication interface. They are respectively connected to the corresponding communication pins of the main control module through their respective communication interfaces.

3. The high-precision laser driving circuit according to claim 2, characterized in that, The DAC control module also includes a reference voltage output module consisting of a current-limiting resistor, a capacitor, and a voltage reference chip. The input terminals of the reference voltages of the first digital-to-analog converter and the second digital-to-analog converter are both connected to the output terminal of the reference voltage output module.

4. The high-precision laser driving circuit according to claim 1, characterized in that, The driving voltage generation module includes a four-stage operational amplifier circuit; The first-stage operational amplifier circuit is a voltage follower circuit. The non-inverting input terminal of the first-stage operational amplifier circuit is used as the first input terminal to connect to the reference voltage, and the output terminal is connected to the inverting input terminal of the second-stage operational amplifier circuit to achieve impedance isolation between the DAC control module and the subsequent circuit. The second-stage operational amplifier circuit is a voltage inverting circuit. The non-inverting input terminal of the second-stage operational amplifier circuit is connected to a reference voltage source, and the output terminal is connected to the inverting input terminal of the third-stage operational amplifier circuit. This is used to invert the output voltage of the first-stage operational amplifier circuit with the reference voltage provided by the reference voltage source as the center. The third-stage operational amplifier circuit is a voltage conversion circuit. The inverting input terminal of the third-stage operational amplifier circuit is used as the second input terminal to connect to the bias voltage, the non-inverting input terminal is connected to the reference voltage source, and the output terminal is connected to the non-inverting input terminal of the fourth-stage operational amplifier circuit, which is used to realize level inversion and superposition of the bias voltage. The fourth-stage operational amplifier circuit is a low-pass filter and buffer amplifier circuit. The output terminal of the fourth-stage operational amplifier circuit is connected to the constant current drive module, which is used to perform low-pass filtering and proportional amplification on the output voltage of the third-stage operational amplifier circuit to obtain the drive voltage, and to achieve impedance isolation from the subsequent circuit.

5. The high-precision laser driving circuit according to claim 4, characterized in that, The constant current drive module includes a first operational amplifier and a sampling resistor. The sampling resistor is connected in series in the current loop of the laser drive circuit. One end of the sampling resistor is connected to the inverting input terminal of the first operational amplifier. The output terminal of the fourth-stage operational amplifier circuit is connected to the non-inverting input terminal of the first operational amplifier, which is used to linearly convert the drive voltage output by the fourth-stage operational amplifier circuit into the corresponding laser drive current.

6. The high-precision laser driving circuit according to claim 5, characterized in that, The feedback module includes a first voltage follower sampling unit and a second voltage follower sampling unit; The first voltage follower sampling unit includes a second operational amplifier, and the non-inverting input terminal of the second operational amplifier is connected to the high potential terminal in the current loop of the laser driving circuit through a first resistor; The second voltage follower sampling unit includes a third operational amplifier, the non-inverting input of which is connected to a low-potential terminal in the current loop of the laser driver circuit via a second resistor.

7. A control method for a high-precision laser driving circuit, applied to the high-precision laser driving circuit according to any one of claims 1 to 6, characterized in that, The method includes: The DAC control module receives control signals output by the main control module; The DAC control module includes a first digital-to-analog converter unit that converts the corresponding control signal into a first analog voltage and inputs it to the first input terminal of the drive voltage generation module. The DAC control module also includes a second digital-to-analog converter unit that converts the corresponding control signal into a second analog voltage and inputs it to the second input terminal of the drive voltage generation module. The first analog voltage is the reference voltage of the laser drive current, and the second analog voltage is the bias voltage of the laser drive current. The driving voltage generation module generates and outputs the driving voltage corresponding to the laser driving current based on the reference voltage and the bias voltage. The constant current drive module receives the drive voltage, converts the drive voltage into a corresponding laser drive current to drive the laser to emit laser light, and outputs the laser drive current to the feedback module. The feedback module acquires the laser drive current, converts the laser drive current into a corresponding sampling voltage signal, and feeds it back to the main control module, so that the main control module adjusts the first analog voltage and the second analog voltage output by the DAC control module according to the sampling voltage signal.

8. The control method for the high-precision laser driving circuit according to claim 7, characterized in that, The driving voltage generation module includes a four-stage operational amplifier circuit; The step of the driving voltage generation module generating and outputting the driving voltage corresponding to the laser driving current based on the reference voltage and the bias voltage includes: The non-inverting input of the first-stage operational amplifier circuit serves as the first input, receiving the reference voltage output by the DAC control module and performing voltage following processing to obtain the following voltage, thereby achieving impedance isolation between the DAC control module and the subsequent circuit. The second-stage operational amplifier circuit, based on the reference voltage provided by the reference voltage source, inverts the follower voltage output by the first-stage operational amplifier circuit to obtain the first output voltage. The inverting input terminal of the third-stage operational amplifier circuit is used as the second input terminal, and the bias voltage output by the DAC control module is connected to it. At the same time, the first output voltage is also connected to it. Based on the bias voltage and the first output voltage, the second output voltage is generated. The fourth-stage operational amplifier circuit performs low-pass filtering and proportional amplification on the second output voltage to obtain the driving voltage and achieves impedance isolation from the subsequent circuit.

9. The control method for the high-precision laser driving circuit according to claim 8, characterized in that, The second-stage operational amplifier circuit, based on a reference voltage provided by a reference voltage source, inverts the follower voltage output from the first-stage operational amplifier circuit to obtain the first output voltage. The steps include: Based on the reference voltage VREF provided by the reference voltage source and the follower voltage Vin output by the first-stage operational amplifier circuit, the first output voltage Vout1 is calculated according to the following formula: Vout1=VREF-(Vin-VREF)=2VREF-Vin.

10. The control method for the high-precision laser driving circuit according to claim 9, characterized in that, The step of generating a second output voltage based on the bias voltage and the first output voltage includes: Based on the bias voltage VI_set2 and the first output voltage Vout1, the second output voltage Vout2 is calculated according to the following formula: Vout2=-(A x Vout1+B x VI_set2)+C; Wherein, A, B, and C are constants determined by the peripheral resistor network of the third-stage operational amplifier circuit, the absolute value of A is less than 1, and A and B are positive numbers.

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